1. Field of the Invention
The present invention relates to an imaging lens assembly, and more particularly, to a compact imaging lens assembly used in a mobile phone camera.
2. Description of the Prior Art
In recent years, with the popularity of mobile phone cameras, the demand for compact imaging lenses is increasing, and the sensor of a general photographing camera is none other than CCD (charge coupled device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, as advanced semiconductor manufacturing technology has allowed the pixel size of sensors to be reduced and the resolution of compact imaging lenses has gradually increased, there is an increasing demand for compact imaging lenses featuring better image quality.
A conventional lens assembly for mobile phone cameras, such as the one disclosed in U.S. Pat. No. 7,145,736, generally comprises three lens elements including, in order from an object side to an image side: a first lens element with positive refractive power; a second lens element with negative refractive power; and a third lens element with positive refractive power. However, the three-element lens has become insufficient for a high-end imaging lens assembly due to the reduction in the pixel size of sensors and the increasing demand for compact lens assemblies featuring better image quality.
U.S. Pat. No. 7,365,920 has disclosed a four lens element assembly where the first and second lens elements form a doublet by their glass spherical surfaces adhering to each other and thereby to correct the chromatic aberration. Such an arrangement of optical elements, however, has the following disadvantages: (1) the freedom of the system is curtailed due to the employment of excess number of spherical glass lenses, thus the total track length of the system cannot be reduced easily; (2) the process of adhering the glass lenses together is complicated, posing difficulties in manufacture.
Therefore, a need exists in the art for an imaging lens assembly that requires simple manufacturing process, maintains a moderate total track length and is applicable to high-resolution mobile phone cameras.